Combat rating system
Patch 2.0.1 introduced a new mechanic: combat ratings. These ratings are for combat stats (on items) that were previously percentage-based. Such as: critical strike chance, hit chance, dodge chance and defense skill. They were introduced because percentage based itemization would have scaled excessively when The Burning Crusade was released and the player cap rose to 70. Combat Rating types The following combat ratings are currently in use: Combat skills Unlike fixed percentages such as 2% critical strike chance, combat ratings diminish in potency as your character increases in level. 2% crit is the same at every level, while 28 critical strike rating grants 4% crit at level 34, 2% crit at level 60, and 1.27% crit at level 70. This allows Blizzard the ability to create and add new and better items to the world without eventually reaching a point where every character has a 100% chance to critically strike. Below are the conversion for level 60, level 70, and level 80 combat skills: Prior to patch 2.0.1, Weapon Skill reduced the percentage of damage lost due to glancing blows. Between patch 2.0.1 and patch 2.3, Weapon Skill gave player +0.1% to their critical strike rating per weapon skill against monsters above their level. As of patch 2.3, all items which previously had Weapon Skill Rating or Feral Combat Rating now have an equal amount of Expertise Rating. From the 2.3 PTR patch notes: "We have added a new stat and associated rating called expertise and expertise rating. Expertise rating converts to expertise at the same rate that weapon skill rating formerly converted at. Each point of expertise reduces the chance for your attacks to be dodged or parried by 0.25%." Unlike Weapon/Feral Combat Rating, Expertise does not have diminishing returns beyond 20 rating. For players, this means that once the hit cap has been reached, one can begin stacking Expertise to increase damage potential against mobs with high dodge/parry. Melee DPS classes won't benefit much from the -parry (as they should be behind the target), however dodges do make up a considerable chunk of lost damage. Druid tanking items with Expertise, such as Earthwarden, will be more valuable for consistent threat generation since a parried/dodged Mangle can be devastating. Since Expertise is 'capped' by the target's chance to dodge/parry, the ideal rating varies per mob. The average level 73 boss has a 6.5% chance to dodge. Completely negating a 6.5% chance to dodge would require 102 Expertise rating at level 70. Defense skills The impact on the defense skill system is slightly more complicated. This skill actually grants a percentage-based benefit already; every 25 points of defense skill grants a 1% dodge chance, 1% parry chance, 1% block chance, 1% increased chance to be missed and 1% decreased chance to be critically hit by physical attacks. Below are the defense rating values needed to achieve 1% of each effect: * Parry was changed in the 2.1 patch to require 25% less rating to equal 1% Parry. The old value at 70 was 31.54 rating for 1%. All of these Ratings have the same "point cost" when determining the level of an item. (See the article on Item values for an in-depth discussion.) For comparison, 1 point of Block Value, which decreases the damage taken when a block occurs by 1, costs 0.65 as much as 1 point of any of these Ratings. Resilience Resilience reduces the effects of all types of critical hits (both physical and spell crits from players or mobs). Resilience has three components; it reduces the chance you will be critically hit by x''%, and it reduces the damage dealt to you by crits that land by 2''x% and finally damage taken from DoTs is reduced by x''%. ''x is the percentage resilience granted by a given resilience rating. In 2.4 an additional effect was added to resilience. It reduces the amount of mana drained or burned by mana draining effects by 2''x''%. PvE tanks usually have high enough +defense values so that mobs won't crit them at all, thus in PvE this is not an important statistic for warriors, but for druids this is another story, see note below. Note: For feral tanking druids, resilience can be more useful than defense to reach crit immunity, 2.6% crit to overcome at lvl 70 with Survival of the Fittest. This is no longer true as of patch 3.0, where druids can become crit immune though SotF alone, without defense or resillience. The formulas are still valid if you don't have 3/3 of this talent. 60 defense rating = (-1%crit,+1%miss,+1%dodge,+1%parry,+1%block) 39.4 resilience rating = (-1%crit,-2%crit damage) 14.7 agi = (+1%dodge,+0.58%crit,+29.4 armor) The conclusion is that if your goal is to become a crit-immune druid, you can swap 60 defense rating for 39.4 resilience rating + 29.4 agi. This is because (1%miss and 1%dodge) = 2%dodge, see also Attack Table for this. So this tradeoff gives you the same crit immunity and gives even slightly better damage mitigation because of the use of Agility. This trade-off is also good for the extra crit and armor, which are both useful for feral tanks. Looking at normal stats of defense rating and resilience on armor and weapons, it is easier to get crit immunity through resilience than through defense. This is not true for Warriors and Paladins as they can Block and Parry and therefore get much more benefit from defense rating than feral druids. Leveling Each time you go up a level, the amount of rating needed to get the same benefit will increase. An example of the scaling involved would be the current implementation of Agility which has always worked this way in the live game, requiring more agility for the same critical strike chance as you go up in level. Diminishing returns As of patch 3.0.1 combat ratings now have diminishing returns. The exact details are noy yet fully understood. See the discussion on the EJ forum. and the blue post about it. Combat Ratings formula The following formulas give the amount of rating required to achieve a 1% bonus. They can be derived from two sources, the values stored in the client and extensive testing done by the author of the Rating Buster addon, and are completely accurate (each method gives the same values within the margin of error for 32-bit floating point precision, or 10^-7). All values except Dodge chance are calculated with below formulas. Level 1 to 10: base 26 Level 10 to 60: level - 8 base --------- 52 Level 60 to 70: 82 base --------------- 262 - 3 * level Level 70 to 100: level + 12 base ---------- 52 Level 70 to 80: 82 base ---- * (131/63)^((level-70)/10) 52 The 70-to-80 formula may change during beta testing, but is current as of Patch 3.0.2.8905 (Aug 8, 2008) . Since Patch 2.1 Dodge and since Patch 2.4.2 Block, Parry and Defense chance are calculated as: Level 1 to 34: base 2 Level 34 to 60: level - 8 base --------- 52 Ratings calculators Ingame * Rating Buster, an addon which shows and calculates Combat ratings on your items (Curse | WoWInt). Online AmpWow has an online calculator. http://www.ampwow.com/wow/viewRatings This does not work in Firefox 2.0.0.3 and works fine in Internet Explorer 6 SP2 and 7.0. Excel Simply enter your current stat ratings and level in the appropriate cells, and all the math is done for you. Ratings Calculator Historical note Prior to version 2.0.1, item bonuses didn't use the Combat Ratings System. Instead, items had equip and on-use bonuses that increased the underlying value directly. For example, instead of increasing the wearer's Crit Rating by 14 and the wearer's Dodge Rating by 12, the old pre-2.0.1 Stormshroud Shoulders added +1% to the wearer's Crit chance and +1% to the wearer's Dodge chance. When Blizzard made the conversion to 2.0.1, all existing items with the old +crit%, +defense, etc. values were converted to their equivalent values in the new Ratings system scaled for a level 60 character. For example, an item that previously gave +10 Defense Skill now gives +15 Defense Rating. (Conversions that would have resulted in a fractional Rating were rounded down to the nearest whole number; e.g. an item that previously gave +3 Defense Skill now gives +4 Defense Rating.) See also * Formulas:Item Values * Attack table References Category:Formulas and game mechanics